For braking and catching a lift car of a lift facility, different mechanisms are known which can be realized by suitable braking devices.
For providing strong compression forces, for example, for a brake and for being able to release these forces in the so-called fail-safe mode and thus in a fail-safe or failure-resistant operation, commonly electromagnets are used as described in the document DE 100 49 168 A1, for example. However, those have the disadvantage that large release gaps can not be realized between friction pads which here are actuated by a coil arrangement and that the weight of the brake is relatively high.
Spring systems can be used in order to realize larger release gaps. One example of those are spring brake actuators having coil springs such as those used in cranes or other industrial facilities in the case of the document DE 197 19 079 C1. However, such brakes are relatively heavy and require a noisy pneumatic or hydraulic release mechanism which is susceptible to leakage and/or contamination so that they do not allow the use of safe drives for releasing these brakes.
A braking device known from the document DE 202 16 046 U1 includes a disc brake which can equally be used as a linear brake, however, wherein the braking force is directly applied by lever arms. In this braking device, it is provided that the complete release system does not include any self-locking components in order to satisfy the requirement of a safety brake. For providing large release gaps, such spring arrangements require a high release force, though, and furthermore the actuation time in the case of a failure of the power supply is long.
A braking device with which a large release gap can be realized is described in the document DE 100 15 263 A1. In this device, linear movements of a drive unit are used so that brake pads of this braking device can travel relatively large distances. Here, a linear unit is used simultaneously to generate a compression force for the brake pads. However, this braking device has no fail-safe function.
If in the present state of the art a fail-safe brake having the corresponding release gap is to be realized, it would have to actuate very rapidly in order to be able to carry out emergency-brake functions. However, this causes a very high noise level. A slow and thus quiet application in the normal operating condition, i.e. when no dangerous situation exists, is not possible in this case.
So-called catching devices with which an instantaneous stopping can be caused are realized in the current state of the art by so-called wedge brakes. Herein, as described in the document EP 1 719 730 A1, for example, a braking wedge is applied to the rail of a lift facility via a countersurface. By the friction generated at the rail, a countersurface of the braking wedge is further drawn in and thus generates the necessary compression force for braking the lift car. Energy stored by springs or weights is in this case only used for safely applying the braking wedge so that it generates the braking force due to the geometry and the kinematics of the entire system. Such catching devices usually generate the required braking energy by generating friction forces at the rail by the braking wedge or its countersurface. Another method for reducing the kinetic energy of the lift car is based on the fact that the braking wedge or the countersurface carries out deformation work at a rail of the lift facility. Hereby, large amounts of energy can be reduced relatively easily.
An alternative to this catching device is described in the document EP 1 283 189 A1. Here, a pull-in lever assuming the function of the braking wedge in conventional braking is used for the generation of the compression force. This pull-in lever has the function of being clamped and pulled in by its geometry and arrangement and thereby to generate a high compression force when a lift car is caught.